Conclusions

Based on a series of experiments on artificial sprinkling of tree species, maximum values of specific moisture retention on the leaf surface area were determined. The specific retention mass per 1 m2 of leaf surface was determined by the nature of leaf surface area and, primarily, by venation type. Leaves with pinnately-netted venation (elm, bird cherry tree) were observed to have 2–3 times higher retention values (180–200 g/m2) as compared to leaves with pinnate venation (birch, aspen; 27–100 g/m2). Total retention mass was determined by leaf surface area during rainfall as well as age and stand height which is different for various tree species.
During the experiments, the leaf surface area was determined for the ”normal” leaf surface in a representative sample (statistical parameters of the leaf area i. e. average, coefficients of variation and asymmetry were determined for the sample). The number of leaves on the experimental branch was determined manually. Statistical errors of total area determination did not exceed 11%. Errors of determining the mass of moisture retained were 4.3%.
The obtained values expressed in the characteristics of the layer of precipitation retained by canopies were visualized on maps. Such maps based on the methodology developed by the authors can be used to calculate water balance elements of mixed forest areas, maximum rainfall discharge from forest watershed. In addition, taking into account the fact that rain precipitation retained by canopies is consumed only for evaporation, this method of estimating the spatial distribution of rainfall losses can be used to estimate monthly amounts of liquid precipitation as corrections to daily rainfall values.
Based on the experiments on artificial branch sprinkling, the parameters of dependency of the leaf surface area (LA, m2) on the maximum mass of retained water (m, d) were established. On the basis of the dependencies and the data on the leaf surface area of the estimated watersheds it is possible to calculate the interception value during a rainfall as well as evaporation losses from the canopy area distributed in space.
The precipitation observations made under coniferous canopies (by four rain gauges) and in open areas (by one rain gauge) in the October of 2017 confirmed the calculated water retention values. According to the data provided by field rain gauges M-99, it was found that the spruce canopies (80 years, bonitet class II) intercept 2-4 mm of rainfall. Meteorological observations need to be continued with the involvement of rain recorders (pluviographs).
The method developed by the authors for estimating and mapping irrecoverable rainfall losses by tree canopies can be used in modeling the flood runoff of small rivers in the Ural forest zone. Taking into account the value of irrecoverable precipitation losses from the stand canopies allows us to increase considerably the accuracy of flood flow calculations for small rivers using genetic methods.